Preparing a wafer for electroplating

ABSTRACT

A wafer is prepared for electroplating via a spin, rinse and dry process performed on the wafer prior to electroplating. The process may be performed in a standalone tool or may be performed in a preclean module integrated into an electroplating tool.

BACKGROUND

[0001] The present invention relates to the manufacture of semiconductordevices and more particularly to the preparation of a wafer forelectroplating.

[0002] Manufacture of semiconductor devices typically involves a seriesof processes in which various layers are deposited and patterned on asubstrate to form a device of the desired type. Semiconductor devicesare typically formed from a semiconductor wafer which can have aplurality of individual dice, each of which includes the circuitry foran individual device. One problem in the manufacture of devices from awafer is that a defect on the wafer, which may occur at any stage of themanufacturing process, can render useless the die or dice containing thedefect.

[0003] Certain semiconductor devices, particularly advanced integratedcircuits of the 0.18 micron (μm) technology node and beyond, have ametal layer electroplated thereon during manufacture. Such a metallayer, which is typically copper, may be used for interconnections. As aresult of the electroplating process, wafers often have one or moredefects. One type of defect commonly occurring as a result of theelectroplating process is a comet defect, which is a defect thatgenerally appears with a comet-like pattern, namely an eye with afollowing tail. A comet defect, along with other defects, can causeappreciable number of dice on a wafer to be rendered useless. Thus aneed exists to reduce or eliminate this and other defects.

[0004] A further problem in the manufacture of semiconductor devices isthat the various processes required are time consuming and may involvethe use of a number of different pieces of equipment and/or tools.Because of this, the throughput, or the number of wafers capable ofbeing processed during a given time frame, is reduced. Thus a needexists to increase throughput and enable high volume wafer processing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is an isometric view of a spin rinse dry (SRD) module inaccordance with one embodiment of the invention.

[0006]FIG. 2 is a partial cutaway view of the SRD module in accordancewith one embodiment of the invention.

[0007]FIG. 3 is a cross section view of the SRD module in accordancewith one embodiment of the invention.

[0008]FIG. 4 is a top view of a semiconductor tool having a precleanmodule in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

[0009] As discussed above, the manufacture of semiconductor devicesrequires many different processing stages. For devices implementing ametal layer, one manner of depositing the metal is by electroplating,also known as electrochemical deposition (ECD). Such electroplating maybe used to deposit, for example, a copper (Cu) layer onto the substrate(generally over preformed layers). Although Cu electroplating will bediscussed herein, it is to be understood that embodiments of the presentinvention may be used with the electroplating of other metals such asaluminum and the like.

[0010] A defect that may result from the formation of a copper layer isa comet defect. The comet defect has minimal Cu deposition in the eye ofthe comet, leading to missing metal after further processing, such aschemical mechanical polishing (CMP). This missing metal may cause anopen circuit for the metal line covered by the defect. As discussedabove, such a defect can impact or “kill” one or more of the productiondie on a wafer.

[0011] The Cu electroplating process typically occurs after abarrier/seed deposition process in which a thin Cu seed film is firstdeposited. A physical vapor deposition (PVD) process may be used todeposit the seed layer. Such deposition may occur in a PVD tool. Afterthe seed layer is deposited, an oxidation process may be performed toprovide an oxide layer over the seed layer. Although an oxidation layermay be created by contact with the ambient atmosphere of the fabricationfacility, such a layer may be deposited via chemical vapor deposition(CVD) for uniformity.

[0012] The electroplating process occurs in a different tool than theabove seed deposition and oxidation processes. Because of the processflow in a fabrication facility, a wafer batch may remain idle fordiffering time periods, often more than several days, between the seedand oxidation processes and the later electroplating process. Such adelay increases the chances of defects, particularly comet defects.

[0013] In one embodiment of a process according to the presentinvention, a wafer may be prepared prior to electroplating to prevent orreduce defects such as comet defects. In one embodiment a spin rinse dry(SRD) process may be performed prior to copper electroplating and afterCu seed deposition. In such an embodiment, a wafer is placed into atool, such as a SRD module, and is rinsed with an aqueous solution, suchas deionized (DI) water, while being subjected to spinning at arelatively low rate. While the embodiments discussed herein use DIwater, it is to be understood that other aqueous solutions may be usedin various embodiments. In certain embodiments, the spin rate duringrinsing may be between approximately 60 revolutions per minute (RPM) toapproximately 120 RPM, while other embodiments may encompass higher orlower rates. The rinsing may be performed for various time periods. Incertain embodiments, the rinse time may be between approximately 15 to45 seconds, and more particularly about 30 seconds. Other time periodsmay be desired for other embodiments.

[0014] The DI water may be applied at various flow rates, which incertain embodiments may be approximately 1.5 liters per minute. Otherflow rates may be desired for other embodiments. The DI water cleans thewafer as it spins. The DI water is turned off at the conclusion of therinsing. In some embodiments, after rinsing the wafer may be dried byspinning it at a higher rate. While the rate of spinning may vary, incertain embodiments, the rate may be between approximately 1200 and 1600RPM, and more particularly between about 1350 and 1450 RPM.

[0015] The DI water rinse cleans the wafer surface to reduce oreliminate organic contamination prior to further processing of thewafer. Surface contamination is a precursor for plating defects, such ascomet defects. Such cleaning thus reduces or eliminates a defect modethat “kills” production die.

[0016] In one embodiment, a SRD tool may be a commercially availabletool, such as those available from Applied Materials (Santa Clara,Calif.) or Novellus (San Jose, Calif.), or the tool may be anothercommercially available or custom tool. Such a tool may include at leastone nozzle for delivery of the aqueous solution over the front surface(and rear surface in certain embodiments) of a wafer to be engaged inthe tool. In one embodiment, the wafer may be mechanically held in theproper location in the tool by a spider assembly, for example. Such anassembly may include a plurality of spider legs extending from a centerportion. Adapted on the distal end of each of the spider legs may be aclip assembly having a clip, a capture post and an O-ring, all of whichmay be used to constrain the wafer in its desired position by limitingX,Y,Z movement and wafer slippage. Conventionally, the SRD tool mayinclude other components such as a lift assembly to lift the wafer intothe desired position and an in-station to provide the wafer to anotherlocation.

[0017] In accordance with one embodiment, a SRD tool receives wafersafter a seed deposition process. The wafers are then subjected to aspin, rinse, and dry process as discussed above. After such processing,the wafers are then ready for electroplating. Depending on processcapabilities, the wafers may proceed directly to such electroplating, orthey may be stored prior to electroplating. It is desirable to performsuch electroplating within several days (approximately 48 hours) of theSRD process in order to prevent defects such as comet defects. If, forsome reason, one or more wafers previously subjected to a SRD process isnot electroplated in such time, it may be desirable to prepare the waferfor electroplating by again performing the SRD process.

[0018] In a second embodiment, the SRD process may be performed in situto an electroplating tool. In certain processes, such an embodiment maycreate process efficiencies in addition to cost savings and defectreduction. Such process efficiencies may occur because the wafers needonly be processed within a single tool, thus avoiding the time andeffort associated with causing the wafers to travel to different tools.Also in certain embodiments, the wafers may pass directly from an SRDmodule within the electroplating tool to the electroplating moduleitself, avoiding any delay and potential defects caused by such a delay.Further, the cost of a separate SRD tool can be saved in suchembodiments.

[0019] Referring now to FIG. 1, an isometric view of SRD module 200 inaccordance with this second embodiment is shown. SRD module 200 isdesigned to be an integrated preclean module for another tool, such asan electroplating tool. The SRD module 200 includes a bowl 210, whichmay be, for example, aluminum. Within the bowl 210 may be a plasticinsert 215. SRD module 200 also includes chuck 220 for support of thewafer. In one embodiment, the chuck 220 may be a backside vacuum chuckwhich supports the wafer. Further support for the wafer exists in waferpins 230 which are located around the perimeter of the wafer. Althoughonly one such pin is shown in FIG. 1, it is to be understood that threeor more pins may be present. SRD module 200 also includes a rinse arm240 which may be adapted to move from the center of the wafer to theedge and back while providing the aqueous solution. It is to beunderstood that SRD module 200 may have additional components notrelevant to the present discussion.

[0020] Shown in FIG. 2 is a partial cutaway view of SRD module 200 inaccordance with one embodiment showing air flow through the moduleduring the drying process. As shown in FIG. 2, air 310, which may beHEPA-filtered air from a mainframe, passes through the bowl 210 (andacross the surface of a wafer, not shown in FIG. 2). From there, the airexits through exhaust ports 320 and an exhaust plenum 330.

[0021] Now referring to FIG. 3, shown is a cross section view of SRDmodule 200 in accordance with one embodiment showing other aspects ofthe module. Specifically, FIG. 3 shows that the plastic insert 215 maybe located within a first insert 250 which may be made from ceramics orpolyvinylidene fluoride (PVDF), in certain embodiments. The module 200may also include an inner ring 260, which may also be made from PVDF.Further, module 200 also includes conventional electromechanical devicesto provide for wafer support and movement. These devices may includespindle 270, lift pin 280, and pin lift mechanism 285. In variousembodiments, SRD module 200 may be commercially available from AppliedMaterials, Novellus, or another supplier, or it may be a custom tool.

[0022] As discussed above, SRD module 200 is desirably located inanother tool to avoid process delays and expense. In one embodiment, SRDmodule 200 may be located within a Cu electroplating tool, such as theIECP™ tool commercially available from Applied Materials.

[0023] In operation, SRD module 200 may process wafers in accordancewith one embodiment of the invention as follows. The wafers are placedin SRD module 200 and grabbed with wafer chuck 220. The wafer is thenspun, and rinsed with DI water flowing from rinse arm 240. In certainembodiments, the rinse arm 240 may move from the wafer center to theedge of the wafer and back again. After rinsing, the wafer is then driedby spinning at a higher speed. In certain embodiments, such spin rinsedry processes may be performed in accordance with the parametersdiscussed above.

[0024] Referring now to FIG. 4, shown is a top view of an electroplatingtool 300 in accordance with one embodiment of the present invention.Although shown with certain modules covered, FIG. 4 provides anindication of wafer flow through electroplating tool 300, namely fromentry port 305 to exit port 340. As shown in FIG. 4, electroplating tool300 includes preclean module 308 which, in this embodiment may beimplemented with two of the SRD modules 200 discussed above.Electroplating tool 300 also includes a plurality of plating cells 310which may be used to electroplate a metal onto desired portions of thewafers. Also included in electroplating tool 300 is a plurality of SRDmodules 320, which may be used to spin rinse and dry the wafers afterthe electroplating process is performed. The electroplating tool 300also includes one or more transport mechanisms which may be used totransport the wafers between the various modules of the tool 300. Asshown in FIG. 4, such transport mechanisms may include robotic member315 adapted to transfer wafers 325 between preclean module 308, platingcells 310, and SRD modules 320. Additional transport mechanisms, such asfront opening universal pods 335 (FOUPs) may be adapted to transferwafers 325 to the exit port 340 after processing in SRD modules 320.

[0025] In the embodiment shown in FIG. 4, because preclean module 308 isin situ, the wafers may proceed directly to electroplating module 310from preclean module 308. Thus this embodiment cleans/prepares the wafersurface in-situ, just prior to the electroplating process. Suchprocessing may save money and increase wafer throughout though the toolto enable high volume manufacturing. In certain embodiments, toolthroughput may increase significantly. For example, use of precleanmodule 308 in certain embodiments may increase tool throughput to aboveapproximately 50 wafers per hour. That is, in certain embodiments, awafer may be subjected to a SRD process and then electroplated within ashort time period, often between about one to ten minutes.

[0026] After electroplating, the wafers may be provided to SRD modules320 for a final spin, rinse, and dry prior to leaving electroplatingtool 300. In the embodiment shown in FIG. 4, SRD modules 320 cannot beused to preclean the wafers prior to plating, as tool 300 requires aprocess flow from entry port 305 to exit port 340. Thus in oneembodiment, provision of preclean module 308 may be used tosignificantly increase wafer throughput through electroplating tool 300,and reduce or prevent common wafer defects such as comet defects.

[0027] While the present invention has been described with respect to alimited number of embodiments, those skilled in the art will appreciatenumerous modifications and variations therefrom. It is intended that theappended claims cover all such modifications and variations as fallwithin the true spirit and scope of this present invention.

What is claimed is:
 1. A method comprising: rinsing a wafer with anaqueous solution; drying the wafer; and electroplating a metal onto atleast a portion of the wafer after rinsing the wafer and drying thewafer.
 2. The method of claim 1, wherein electroplating the metalcomprises electroplating copper.
 3. The method of claim 1, furthercomprising depositing a metal seed layer onto the portion of the waferprior to rinsing the wafer.
 4. The method of claim 1, wherein rinsingthe wafer comprises applying deionized water to the wafer.
 5. The methodof claim 2, further comprising using the copper for interconnections. 6.The method of claim 1, further comprising preventing comet defects onthe wafer by rinsing the wafer and drying the wafer.
 7. The method ofclaim 2, further comprising electroplating the metal within 48 hoursafter rinsing the wafer and drying the wafer.
 8. The method of claim 1,further comprising spinning the wafer while rinsing the wafer and dryingthe wafer.
 9. A method comprising: placing a wafer in a spin rinse drymodule integrated within a tool; rinsing the wafer with an aqueoussolution; drying the wafer; and electroplating a metal onto at least aportion of the wafer after rinsing the wafer and drying the wafer. 10.The method of claim 9, further comprising transporting the wafer to anelectroplating module integrated within the tool to electroplate themetal.
 11. The method of claim 9, further comprising depositing a metalseed layer onto the portion of the wafer prior to rinsing the wafer. 12.The method of claim 9, wherein rinsing the wafer comprises applyingdeionized water to the wafer.
 13. The method of claim 12, furthercomprising providing the deionized water from a center of the wafer toan edge of the wafer.
 14. The method of claim 9, further comprisingspinning the wafer while rinsing the wafer and drying the wafer.
 15. Themethod of claim 10, further comprising electroplating the metal withinten minutes after rinsing the wafer and drying the wafer.
 16. Anapparatus comprising: a semiconductor tool having at least a firstmodule and a second module integrated therein; the first modulecomprising a spin rinse dry module to spin, rinse, and dry a wafer; thesecond module comprising an electroplating module to electroplate ametal onto at least a portion of the wafer; and a transport mechanism todeliver the wafer to the electroplating module from the spin rinse drymodule.
 17. The apparatus of claim 16, wherein the electroplating modulecomprises a copper electroplating module.
 18. The apparatus of claim 16,wherein the first module comprises an introduction mechanism to providean aqueous solution to the wafer.
 19. The apparatus of claim 16, whereinthe first module is stationed adjacent an entry port of thesemiconductor tool.